Thin film transistor liquid crystal displays (TFT-LCDs) have such advantages as small volume, low power consumption, free of radiation and low manufacture cost, and have dominated position in the current planarization panel display market. A liquid crystal panel is an important component in the liquid crystal display. As shown in FIG. 1 and FIG. 2, the liquid crystal panel includes a color filter substrate 1 and an array substrate 2 which is oppositely arranged with respective to the color filter substrate 1 to form a cell. A sealed space is formed between the color filter substrate 1 and the array substrate 2 through a sealant 4. The sealed space is filled with liquid crystal. A black matrix 3 is formed on the color filter substrate, and is configured to define a plurality of subpixel regions in a display region 100. A filter layer (i.e., a red filter layer 31, a green filter layer 32, a blue filter layer 33 and a white filter layer 34) configured to transmit light of specific colors is disposed in the subpixel regions to realize color display. A planarization layer 20 is covered on the black matrix 3 and the filter layer. The presence of the black matrix 3 can prevent light leaking and occurrence of color crosstalk in adjacent subpixel regions.
In the related art, the black matrix may be distributed in two modes in which edges of the black matrix are flush with edges of the color filter substrate, or not flush with the edges of the color filter substrate. For the mode in which the edges of the black matrix are not flush with the edges of the color filter substrate, there is a distance of 0.2 μm˜0.4 μm between edges of the black matrix and the edge of the color filter substrate. In this mode, there is a problem of light leaking from a periphery of the liquid crystal panel when the liquid crystal panel is in a dark state. Particularly, there is a dense region having a large amount of parallel metal wirings at a position close to the edge, this problem is more serious. For the mode in which the edges of the black matrix are flush with the edges of the color filter substrate, the problem of light leaking from the periphery of the liquid crystal panel when the liquid crystal panel is in a dark state is not existed.
For a TFT-LCD which takes a transverse electric field to drive liquid crystal molecules to deflect, both a common electrode and a pixel electrode are formed on the array substrate. Typical material for the black matrix has a resistance value of about 106Ω˜107Ω, and is not a complete insulator. A resistance value of material for the planarization layer is much larger, about 1015Ω˜1016Ω. For a TFT-LCD of large size, a common voltage and a pixel voltage are usually high. The black matrix can induce a certain amount of charge due to the capacitor effect, i.e., there is a certain induced voltage. After testing, the block matrix has an induced voltage of about +5V˜+7V, which is close to a pixel voltage or a voltage (Vcom, about +8V) of the common electrode when the liquid crystal panel is in a dark state. However, for the black matrix with edges flush with the edges of the color filter substrate, the black matrix is easily grounded or contacts other low voltages, and then the charge is discharged, which leads to a drop of the induced voltage of the block matrix, resulting in that a voltage difference between the induced voltage and the pixel voltage, or between the induced voltage and the voltage of the common electrode is increased. As a result, liquid crystal molecules are deflected and pixels become bright. Since green pixels are much brighter, thus, a phenomenon such as becoming green occurs in the dark state, which seriously affects product quality.